Re: [PATCH 2/2] platform/x86/amd: hfi: Stand down when amd-pstate CAS is active

[Mario Limonciello]

On 11/14/26 09:03, Vishal Badole wrote:
> From: Krishnamoorthi M <krishnamoorthi.m@xxxxxxx>
>
> When amd-pstate CAS is active, it takes ownership of per-CPU capacity
> values that the scheduler uses to distinguish performance and efficiency
> cores. amd-hfi manages the same scheduler state through its ranking
> mechanism. Running both simultaneously would cause them to overwrite
> each other's settings, leading to unpredictable task placement on hybrid
> platforms.
>
> Avoid loading amd-hfi if CAS is enabled.
>
> Signed-off-by: Krishnamoorthi M <krishnamoorthi.m@xxxxxxx>

When a patch is authored by another person and you send it on their 
behalf you need to add your own S-o-b as well.

Think of it like a chain of custody.

> ---
>   drivers/platform/x86/amd/hfi/hfi.c | 8 ++++++++
>   1 file changed, 8 insertions(+)
>
> diff --git a/drivers/platform/x86/amd/hfi/hfi.c b/drivers/platform/x86/amd/hfi/hfi.c
> index 86a7f4332c35..b6878614e2bc 100644
> --- a/drivers/platform/x86/amd/hfi/hfi.c
> +++ b/drivers/platform/x86/amd/hfi/hfi.c
> @@ -29,6 +29,8 @@
>   
>   #include <asm/cpu_device_id.h>
>   
> +#include <linux/amd-pstate.h>
> +
>   #include <acpi/pcc.h>
>   #include <acpi/cppc_acpi.h>
>   
> @@ -536,6 +538,12 @@ static int __init amd_hfi_init(void)
>   	    !cpu_feature_enabled(X86_FEATURE_AMD_WORKLOAD_CLASS))
>   		return -ENODEV;
>   
> +	/* amd-pstate CAS owns heterogeneous core scheduling when enabled. */
> +	if (amd_pstate_cas_active()) {
> +		pr_debug("amd-pstate CAS is active, not loading amd-hfi\n");
> +		return -ENODEV;
> +	}
> +
>   	ret = platform_driver_register(&amd_hfi_driver);
>   	if (ret)
>   		pr_err("failed to register HFI driver\n");